The present invention relates to a centralized lubrication system for providing a grease or oil lubricant to a plurality of bearing points used in a multitude of industrial and commercial applications. Although the prior art teaches many systems for centralized lubrication of multiple bearing points, all of these teachings demonstrate limitations that the present invention addresses and overcomes.
Centralized automatic systems for providing lubrication to various moving parts such as bearings in machinery are generally known in the art. These systems allow for predetermined quantities of common lubricants such as grease and oil to be automatically distributed to a plurality of machinery points at regular intervals without the need for manual human intervention.
Prior art lubrication systems are generally either single line progressive (series progressive) or dual line parallel (parallel) in design. Series progressive systems operate by using pistons to move back and forth in a specific bore. A pump pushes lubricant from a reservoir through a single supply line which is connected to a number of metering valves as required for the particular application. As the lubricant reaches a metering valve, a dispensing piston is shifted in one direction to allow the lubricant to flow through the bore directly to the machinery requiring lubrication. There are generally pluralities of dispensing pistons in a block that are connected in series, or one after the other. The function of each distal piston in the system is directly dependant on the immediately proximal piston shifting to permit the flow of lubrication through and past that proximal point. Therefore, if an upstream piston in the series does not shift due to a problem such as a supply line blockage for example, all of the pistons further downstream or distal to that point will not receive a flow of lubrication to shift those pistons and lubricate those distal lubrication points.
U.S. Pat. No. 3,995,717 to Kroffke describes a centralized series progressive lubrication system where several lubricant injectors function in a sequential manor so that each downstream injector is fed only when the immediately corresponding piston is displaced by the flow of lubricant past that point in the system. This invention combined a system of lubricant feeders connected in series with corresponding injectors to deliver the lubricant to a plurality of points in sequence. This combination allows for the addition of additional injectors as needed without redesigning the entire feeder supply system but while still maintaining a sequential pattern of lubrication to points in the system.
In another example of a series progressive centralized lubrication system, U.S. Pat. No. 4,105,094 to Callahan utilizes a single line to supply lubrication to a plurality of bearing points arranged in series. As in the Kroffke patent, the downstream points only receive a supply of lubrication when the preceding piston in the supply line is displaced allowing lubricant to flow past to the bearing point and the next piston in the series. Once all of the points receive lubrication, a single check valve at the end of the system operates and the flow of lubricant reverses to return unused lubricant back through the same line.
Parallel automatic lubrication systems utilize two lines to move hydraulically adjustable valves or pistons and permit flow of lubricant to a plurality of machinery points. In this system, a pump pressurizes one of the lines while simultaneously venting the second line in the system. Once the system is pressurized, metering valves operate simultaneously to lubricate bearing points. Since each bearing point is lubricated simultaneously, the distal points are not directly dependant on the function of pistons up stream or proximally located in the system. Once a specific pressure is attained, the pump disengages and a valve opens to redirect the remaining lubricant through the second line in the system which functions as a return line to the reservoir. However, the next time that the pump pressurizes the system, the lines reverse uses and the second line becomes the distribution line and the first line becomes the return line.
An example of a two line system is described in U.S. Pat. No. 4,390,083 to Saretzky where a dual conduit system uses two feed conduits to supply lubricant to a plurality of points that require different amounts of lubricant. The two line system has an outlet connected to a progressive distributor control chamber and the pressure inlet connected to the dual feed conduits. This permits the system to provide differing amounts of lubricant to different rubbing points within the system at a single system pressure by adjusting each individual progressive distributor control chamber.
Each of these systems and combination systems has advantages and disadvantages. Series progressive systems are cyclical in operation, so they are easy to monitor for blockages in the line. If a blockage occurs, the locally blocked piston fails to shift and a sensor transmits an alarm. Additionally, since pistons move back and forth in their respective bore, only a single line is necessary to supply lubricant.
However, since these systems work on resistance to flow pressure in series, they will be either significantly limited in length, for example only 3-10 pistons, or be under extremely high pressure due to the viscosity of the lubricants used for industrial applications. Also, since many industrial processes require long machining runs, a system limited in length may not be ideal or practical for many applications. Another disadvantage is that any blockage in the system necessitates shutting down the entire run for repair since they are connected in series under pressure resulting in costly delays.
Parallel systems likewise have advantages and disadvantages. Since metering valves operate simultaneously, a parallel system allows for a much longer run with a larger amount of metering points since there is not a significant drop in the overall system pressure throughout the entire line. This is better suited for many larger industrial machines with a multitude of points or bearings that require lubrication. Also, if a particular point fails, the entire system need not be shut down while a single injector is replaces. This allows for a less costly repair while keeping the machine online and in service.
However, if a blockage does occur in the system, there is no way to know unless a sensor is placed at each lubrication point at increased cost. Unlike in the series system, pump pressure would not increase so there would be no outward sign of failure until the bearing point failed or burned out completely at a much greater expense than replacing only the injector. Additionally, the initial material and installation cost is greater due to the system having more than one line.
Many industrial central lubrication system applications, such as those employed in steel mills, require a longer length system that will have a low pressure drop where failure of a lubrication point is easily identifiable but where replacement of the failed lubrication point will not shut require shutting down the entire system. Therefore, a need remains for a centralized lubrication system capable of lubricating a plurality of bearing points over long runs through a hybrid combination of the above systems.
More specifically, a need still exists for a centralized combination grease and/or oil lubricating system that takes advantage of the benefits of both a series progressive system and a dual line parallel system while overcoming the individual disadvantages of both systems when used alone and method of the same.